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ATC Associates, Inc Project No 99975 7501 1 ' 4.0 REMEDIATION STATUS AND EFFECTIVENESS REPORT Soil vapor extraction(SVE)and groundwater extraction at the site began on February 10, 1994 Since that time, through January 1999 more than 4 million gallons of groundwater and 30 million cubic feet of soil vapor have been extracted from four soil vapor and groundwater co- extraction wells at the site. Prior to discharge to the atmosphere and surface,the soil vapor and groundwater are treated through 2,000-pound vapor phase and aqueous phase carbon units, respectively A log of groundwater production is presented in Table 4 and the groundwater influent and effluent analyses are presented in Table 5 Table 6 is a log of the production and ' analysis of extracted soil vapor The data which are most significant for assessing the progress of the remediation program are ' the groundwater monitoring results presented in Table 2 and Table 7 For the four most severely impacted monitoring wells, Table 7 presents a comparison of the average TPHg and benzene concentrations for samples collected during the three monitoring events prior to the startup of ' the remediation program (in February 1998) with the average results for the three most recent monitoring events These results near show total elimination of total hydrocarbons in most of ' the previously impacted monitoring wells, and reductions of 76-95 percent in the severely impacted monitoring wells BEI-MW3 and BEI-MW 1 Reductions of benzene in these wells are more than 92 percent and 95 percent, respectively A significant observation,regarding the remediation process is the considerable amount of bio- mass evident in the groundwater immediately after its extraction This was particularly apparent ' during the initial months after the remediation program was initiated This occurrence provides evidence that the physical and chemical characteristics for bio-degradation in the groundwater both above and below the surface, are particularly favorable ATC believes the migration of ' fresh oxygenated air and water through the site as a result of the soil vapor and groundwater extraction has effected the removal of far greater amounts of hydrocarbons, by the process of enhanced bio-degradation, than have been recovered above ground in the respective SVE and ' groundwater carbon treatment units ' SVE Radius of Influence Testin During the December 10, 1998 monitoring event,a soil vapor extraction radius of influence test ' was conducted to determine the vacuum influence surrounding the co-extraction well EW-1 As soil vapor was extracted from EW-1, the vacuum influence away from the well was measured at three surrounding monitoring wells While pumping 100 cubic feet per minute from EW-1 — ' the vacuum in the extraction well is only about 3 inches of mercury(39 inches of water) This attests to the relatively high degree of gas permeability in the soil surrounding the well Using supersensitive magnahelix vacuum gauges, the most notable vacuum effect was observed in monitoring well BEI-MW I located approximately 40 feet from the co-extraction well A differential of 0 3 inches of water was observed between the vacuum measured in the well and ambient air pressure The vacuum differential for BEI-MW3, located only about 10-12 feet Groundwater Monitoring and Remediation Status Report Page 2